WO2019049875A1 - Positive electrode active material for alkaline storage battery - Google Patents

Abstract

Provided is a positive electrode active material for an alkaline storage battery having an excellent utilization rate even under a high-temperature condition. The positive electrode active material for an alkaline storage battery includes nickel-containing hydroxide particles containing solid-solutioned cobalt, and a cobalt- containing coating layer coating the hydroxide particles, wherein: the positive electrode active material for an alkaline storage battery have diffraction peaks between diffraction angles of 65°-66° represented by 2θ of a diffraction pattern obtained by X-ray diffraction measurement; among the solid-solutioned cobalts, the content of trivalent cobalt is 30 mass% or more; the proportion of the content ratio of the trivalent cobalt solid-solutioned in the positive electrode active material and having the secondary particle diameter (≤D10) in which the cumulative volume percentage of the secondary particles of 10.0 volume% or less to the content ratio of the trivalent cobalt solid-solutioned in the positive electrode active material is 0.80-1.20; and the proportion of the content ratio the trivalent cobalt solid-solutioned in the positive electrode active material and having the secondary particle diameter (≥D90 or more) in which the cumulative volume percentage of the secondary particles of 90.0 volume% to the content ratio of the trivalent cobalt solid-solutioned in the positive electrode active material is 0.80-1.20.

Description

Positive electrode active material for alkaline storage battery

The present invention relates to a positive electrode active material used for a positive electrode of an alkaline storage battery, in particular, a positive electrode active material for an alkaline storage battery having an excellent utilization factor even under high temperature conditions.

BACKGROUND ART In recent years, alkaline storage batteries have been used in a wide range of fields such as vehicles because of characteristics such as high current discharge and excellent low temperature characteristics and long life. As a positive electrode active material of an alkaline storage battery, for example, nickel hydroxide particles are used.

On the other hand, alkaline storage batteries are also required to have improved utilization as with other storage batteries, and are also required to be able to exhibit excellent utilization even under high-temperature use conditions.

Therefore, in order to improve the utilization rate of the alkaline storage battery, the positive electrode active material of an alkaline storage battery in which the surface of nickel hydroxide particles is coated with a cobalt hydroxide layer, and cobalt of the cobalt hydroxide layer mainly comprises divalent cobalt. Has been proposed (Patent Document 1). Moreover, in order to suppress the self-discharge of the alkaline storage battery, the surface of the nickel hydroxide particles is coated with a cobalt oxyhydroxide layer, and the cobalt oxyhydroxide layer has a cobalt valence of 2.1 to 3.0. A positive electrode active material of an alkaline storage battery composed of a compound has been proposed (Patent Document 2).

However, although the alkaline storage battery having good utilization and self-discharge characteristics can be obtained by using the positive electrode active materials of Patent Document 1 and Patent Document 2, it may be that a sufficient utilization can not be obtained under a high temperature environment. There was room for improvement.

JP-A-7-320735 JP, 2014-169201, A

In view of the above-mentioned circumstances, an object of the present invention is to provide a positive electrode active material for an alkaline storage battery having an excellent utilization factor even under high temperature conditions.

An aspect of the present invention is a positive electrode active material for an alkaline storage battery, comprising nickel-containing hydroxide particles containing dissolved cobalt and a coating layer containing cobalt that coats the hydroxide particles. X-ray diffraction measurement has a diffraction peak between diffraction angles of 65.degree. And 66.degree. Represented by 2.theta. Of the diffraction pattern, and the content of trivalent cobalt in the solid-solved cobalt is 30%. 2% by mass or less of the cumulative volume percentage of the positive electrode active material for an alkaline storage battery relative to the content of the trivalent cobalt in solid solution of the positive electrode active material for an alkaline storage battery, which is not less than mass% The ratio of the content of trivalent cobalt in solid solution of the positive electrode active material particles for alkaline storage batteries having the following particle diameter (≦ D10) is 0.80 or more and 1.20 or less, and the cumulative volume percentage is 90.0% by volume More than secondary particle diameter ( The positive electrode active material particles for an alkaline storage battery of D90), the proportion of the content of solid-dissolved trivalent cobalt is a positive electrode active material for an alkaline storage battery is 0.80 to 1.20.

An aspect of the present invention is the positive electrode active material for an alkaline storage battery, wherein the diffraction peak is derived from a trivalent cobalt compound represented by CoHO ₂ .

According to an aspect of the present invention, the secondary particle diameter (D90) of the positive electrode active material for an alkaline storage battery having a cumulative volume percentage of 90.0% by volume-the positive electrode active material for an alkaline storage battery having a cumulative volume percentage of 10.0% by volume Positive electrode active material for an alkaline storage battery in which the secondary particle diameter (D50) of the positive electrode active material for an alkaline storage battery having a secondary particle diameter (D10) of: 50.0 volume% in cumulative volume percentage is 0.85 or more is there.

An aspect of the present invention is a positive electrode having the above-described positive electrode active material for an alkaline storage battery.

An aspect of the present invention is an alkaline storage battery provided with the above-described positive electrode.

According to the aspect of the present invention, a secondary volume with a cumulative volume percentage of 10.0% by volume or less of the positive electrode active material for alkaline storage battery relative to the content of trivalent cobalt in solid solution of the positive electrode active material for alkaline storage battery The ratio of the content of trivalent cobalt in solid solution of the particle diameter (≦ D10) of the positive electrode active material particles for alkaline storage batteries is 0.80 to 1.20, and the cumulative volume percentage is 90.0% by volume or more The use of the positive electrode active material particles for alkaline storage batteries having the following particle diameter (≧ D90) is excellent even under high temperature conditions because the ratio of the content of trivalent cobalt in solid solution is 0.80 or more and 1.20 or less The positive electrode active material for an alkaline storage battery having a rate can be obtained.

According to an aspect of the present invention, [secondary particle diameter of positive electrode active material for an alkaline storage battery having a cumulative volume percentage of 90.0% by volume-secondary particle diameter of positive electrode active material for an alkaline storage battery having a cumulative volume percentage of 10.0% by volume] The secondary particle diameter of the positive electrode active material for an alkaline storage battery having a particle diameter] / cumulative volume percentage of 50.0% by volume is 0.85 or more, so that the space between the positive electrode active material for an alkaline storage battery is reduced. In the alkaline storage battery using the positive electrode active material as the positive electrode, the utilization factor at high temperature is excellent, and a good volume capacity can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS It is a graph which shows the diffraction pattern of X-ray-diffraction measurement of Experimental example 1, Experimental example 2, and cobalt oxyhydroxide. It is the elements on larger scale of the graph which shows the diffraction pattern of FIG. It is a graph which shows the diffraction pattern of an X-ray-diffraction measurement of an example, a comparative example, and cobalt oxyhydroxide. It is the elements on larger scale of the graph which shows the diffraction pattern of FIG.

Hereinafter, details of the positive electrode active material for an alkaline storage battery of the present invention will be described.

The positive electrode active material for an alkaline storage battery of the present invention comprises a plurality of primary particles having nickel-containing hydroxide particles containing solid-dissolved cobalt and a cobalt-containing coating layer covering the hydroxide particles. A plurality of positive electrode active material particles for an alkaline storage battery formed by aggregation of particles are contained. The positive electrode active material for an alkaline storage battery has a diffraction peak between diffraction angles of 65 ° and 66 ° represented by 2θ of a diffraction pattern obtained by X-ray diffraction measurement.

Further, in the positive electrode active material for an alkaline storage battery, the content of trivalent cobalt in cobalt dissolved in nickel hydroxide particles is 30% by mass or more, and nickel as a positive electrode active material for an alkaline storage battery An alkaline storage battery having a secondary particle diameter (≦ D10) having a cumulative volume percentage of 10.0% by volume or less in a positive electrode active material for an alkaline storage battery with respect to the content of trivalent cobalt dissolved in hydroxide particles containing The ratio of the content of trivalent cobalt dissolved in nickel hydroxide particles in the positive electrode active material particles for use is 0.80 or more and 1.20 or less, and the cumulative volume percentage is 90.0% by volume or more The ratio of the content of trivalent cobalt in solid solution in the nickel-containing hydroxide particles of the positive electrode active material particles for an alkaline storage battery having the next particle diameter (≧ D90) is 0.80 or more and 1.20 or less.

The positive electrode active material particles for an alkaline storage battery constituting the positive electrode active material for an alkaline storage battery of the present invention have hydroxide particles containing nickel and a coating layer containing cobalt, which covers the hydroxide particles. And has a diffraction peak between diffraction angles of 65 ° and 66 ° represented by 2θ of a diffraction pattern obtained by X-ray diffraction measurement. Further, the hydroxide particles containing nickel contain cobalt in solid solution. The positive electrode active material particles for alkaline storage batteries have, as core particles, particles of a hydroxide containing nickel (Ni), and the core particles are coated with a covering layer containing cobalt. Therefore, a positive electrode active material particle for an alkaline storage battery is a particle having a core-shell structure, and is a cobalt-containing compound-coated nickel-containing hydroxide having a core of hydroxide particles containing nickel and a shell of a compound containing cobalt. It has become a particle.

Although the shape of the said positive electrode active material particle for alkaline storage batteries is not specifically limited, For example, substantially spherical shape can be mentioned.

The cobalt-containing compound-coated nickel-containing hydroxide particles, which are positive electrode active material particles for alkaline storage batteries, are embodiments of secondary particles formed by aggregation of a plurality of primary particles. Although the particle size distribution of the positive electrode active material for an alkaline storage battery of the present invention is not particularly limited, for example, the lower limit value of the secondary particle diameter D50 (hereinafter sometimes referred to as "D50") having a cumulative volume percentage of 50 vol. 2.0 μm is preferable, 3.0 μm is more preferable, and 4.0 μm is particularly preferable. On the other hand, the upper limit value of D50 of the cobalt-containing compound-coated nickel-containing hydroxide particles is preferably 10.0 μm from the viewpoint of the balance between the improvement of density and securing of the contact surface with the electrolyte. In order to further improve the utilization rate of the above, 8.0 μm is particularly preferable. The lower limit value and the upper limit value described above can be arbitrarily combined.

The BET specific surface area of the cobalt-containing compound-coated nickel-containing hydroxide particles is not particularly limited, but, for example, the lower limit value is 5.0 m ^{2 in} terms of the balance between improving the density and securing the contact surface with the electrolyte. / g are preferred, particularly preferably 10.0 m ² / g, the upper limit is preferably 30.0 m ² / g, 25.0 m ² / g is particularly preferred. The lower limit value and the upper limit value described above can be arbitrarily combined.

The tap density of the cobalt-containing compound-coated nickel-containing hydroxide particles is not particularly limited, but is preferably 1.5 g / cm ³ or more, for example, from the viewpoint of improving the filling degree when used as a positive electrode active material. 7 g / cm ³ or more is particularly preferable.

The bulk density of the cobalt-containing compound-coated nickel-containing hydroxide particles is not particularly limited, but is preferably 0.8 g / cm ³ or more, for example, from the viewpoint of improvement of the filling degree when used as a positive electrode active material Particularly preferred is at least ³ cm ³ .

The positive electrode active material particles for an alkaline storage battery, as described above, are cobalt-containing compound-coated nickel-containing hydroxides in which a cobalt-containing coating layer is formed on the surface of nickel-containing hydroxide particles containing solid-dissolved cobalt. It is an object particle. The coating layer containing cobalt contains a compound containing cobalt. Also, the coating layer containing cobalt may cover the entire surface of the hydroxide particle containing nickel, or may cover a partial region of the surface of the hydroxide particle containing nickel.

The mass ratio of cobalt in the coating layer containing cobalt in the cobalt-containing compound-coated nickel-containing hydroxide particles is not particularly limited, but the lower limit thereof is 1 from the viewpoint of further improving the utilization under high temperature conditions. The content is preferably 0% by mass, particularly preferably 2.0% by mass. On the other hand, in the cobalt-containing compound-coated nickel-containing hydroxide particles, the upper limit of the mass ratio of cobalt in the coating layer containing cobalt is preferably 5.0 mass%, particularly preferably 4.0 mass%. The lower limit value and the upper limit value described above can be arbitrarily combined.

Moreover, cobalt of the coating layer containing cobalt is trivalent cobalt.

As the chemical structure of trivalent cobalt, for example, cobalt oxyhydroxide (CoHO ₂ ) (herein, cobalt oxyhydroxide may be simply referred to as “cobalt oxyhydroxide” or “CoHO ₂ ”. Can be mentioned.

The coating layer containing trivalent cobalt has a diffraction peak between diffraction angles of 65 ° and 66 ° represented by 2θ of a diffraction pattern obtained by X-ray diffraction measurement. The diffraction peak is mainly derived from cobalt oxyhydroxide (CoHO ₂ ).

The hydroxide particles containing nickel (Ni) containing solid solution cobalt is not particularly limited as long as it contains nickel (Ni) and cobalt solid solution, but, for example, cobalt hydroxide in nickel hydroxide Particles made by solid solution, at least one transition selected from the group consisting of nickel (Ni) and other transition metal elements (eg, magnesium (Mg), manganese (Mn), zinc (Zn) and aluminum (Al)) The particle etc. in which cobalt carried out solid solution can be mentioned to the hydroxide containing metal element).

The content of nickel in hydroxide particles containing nickel in which cobalt is dissolved in solid solution in the cobalt-containing compound-coated nickel-containing hydroxide particles is not particularly limited, but the lower limit thereof is preferably 40% by mass, 45 % By mass is more preferable, and 50% by mass is particularly preferable. On the other hand, the upper limit value of the content of nickel in hydroxide particles containing nickel in which cobalt is dissolved in solid solution in the cobalt-containing compound-coated nickel-containing hydroxide particles is preferably 60 mass%, particularly 57 mass% preferable. The lower limit value and the upper limit value described above can be arbitrarily combined.

The amount of cobalt dissolved in the nickel-containing hydroxide particles in the cobalt-containing compound-coated nickel-containing hydroxide particles is not particularly limited, but the lower limit thereof further improves the utilization factor under high temperature conditions 0.10 mass% is preferable, 0.20 mass% is more preferable, and 0.50 mass% is especially preferable. On the other hand, in the cobalt-containing compound-coated nickel-containing hydroxide particles, the upper limit of the amount of cobalt solid-solved in the particles of the nickel-containing hydroxide is preferably 5.0% by mass, more preferably 3.0% by mass Preferably, 2.0% by mass is particularly preferred. The lower limit value and the upper limit value described above can be arbitrarily combined.

Further, in the positive electrode active material for an alkaline storage battery of the present invention, at least 30% by mass of cobalt dissolved in nickel hydroxide particles is trivalent cobalt in view of the utilization factor under high temperature conditions. . The lower limit value of the trivalent cobalt content of cobalt dissolved in nickel hydroxide particles is preferably 35% by mass, 40% by mass from the viewpoint of further improving the utilization under high temperature conditions. Is particularly preferred. On the other hand, the upper limit of the content of trivalent cobalt among cobalt dissolved in nickel hydroxide particles is preferably 100% by mass from the viewpoint of obtaining the utilization under further excellent high temperature conditions, 70 mass% is particularly preferable in terms of facilitating the oxidation treatment step from divalent cobalt to trivalent cobalt. The lower limit value and the upper limit value described above can be arbitrarily combined.

The chemical structure of the trivalent cobalt dissolved in the hydroxide particles containing nickel, for example, a cobalt oxyhydroxide (CoHO _2).

As described above, when cobalt oxyhydroxide is solid-solved in hydroxide particles containing nickel, the hydroxide particles containing nickel are also similar to the coating layer containing cobalt oxyhydroxide (CoHO ₂ ) In addition, it has a diffraction peak between diffraction angles of 65 ° and 66 ° represented by 2θ of a diffraction pattern obtained by X-ray diffraction measurement.

Among cobalts dissolved in hydroxide particles containing nickel, examples of cobalt other than trivalent cobalt include divalent cobalt. As a chemical structure of bivalent cobalt, cobalt hydroxide (Co (OH) ₂ ) can be mentioned, for example.

The shape of the nickel-containing hydroxide particles in which cobalt is solid-solved is not particularly limited, and may be, for example, substantially spherical.

About the positive electrode active material for an alkaline storage battery of the present invention having a plurality of cobalt-containing compound-coated nickel-containing hydroxide particles, trivalent cobalt solid-solved in nickel-containing hydroxide particles of a positive electrode active material for an alkaline storage battery Of the positive electrode active materials for alkaline storage batteries with respect to the content, in secondary particle diameter ≦ D10 where cumulative volume percentage is 10.0 volume% or less (hereinafter sometimes referred to as “≦ D10” or “D10 or less”), The ratio of the content of trivalent cobalt solid-solved in hydroxide particles containing nickel is 0.80 or more and 1.20 or less, and it is 0.90 from the viewpoint of obtaining the utilization under excellent high temperature conditions. More than 1.15 is preferred. Furthermore, the cumulative volume percentage of the positive electrode active material for alkaline storage batteries is 90.0% by volume or more with respect to the content of trivalent cobalt solid-solved in hydroxide particles containing nickel, of the positive electrode active material for alkaline storage batteries The ratio of the content of trivalent cobalt solid-solved in the nickel-containing hydroxide particles in secondary particle diameter D D90 (hereinafter sometimes referred to as "≧ D90" or "D90 or more") is 0. It is preferably 80 or more and 1.20 or less, and more preferably 0.90 or more and 1.15 or less from the viewpoint of obtaining an excellent utilization factor under high temperature conditions.

From the above, in the positive electrode active material for an alkaline storage battery of the present invention, in each cobalt-containing compound-coated nickel-containing hydroxide particle, the content of trivalent cobalt solid-solved in the hydroxide particle containing nickel is equalized It is done.

The content of trivalent cobalt among cobalt dissolved in nickel hydroxide particles in D10 or less is not particularly limited, but is the same as the content of trivalent cobalt in the positive electrode active material for alkaline storage batteries or Approximately the same degree is preferable, and therefore, the lower limit thereof is preferably 30% by mass, more preferably 35% by mass, and particularly preferably 40% by mass, from the viewpoint of further improving the utilization factor under high temperature conditions. On the other hand, the upper limit thereof is preferably 100% by mass, and particularly preferably 70% by mass from the viewpoint of further facilitating the oxidation treatment step from divalent cobalt to trivalent cobalt. The lower limit value and the upper limit value described above can be arbitrarily combined.

The content of trivalent cobalt among cobalt dissolved in nickel hydroxide particles in D90 or more is not particularly limited, but the content of positive electrode active material for alkaline storage batteries and trivalent cobalt in D10 or less The lower limit is preferably 30% by mass, more preferably 35% by mass, and particularly preferably 40% by mass, from the viewpoint of further improving the utilization under high temperature conditions. On the other hand, the upper limit thereof is preferably 100% by mass, and particularly preferably 70% by mass from the viewpoint of further facilitating the oxidation treatment step from divalent cobalt to trivalent cobalt. The lower limit value and the upper limit value described above can be arbitrarily combined.

The positive electrode active material for an alkaline storage battery of the present invention is an index showing the spread of particle size distribution [(Secondary particle diameter D90 with cumulative volume percentage of 90% by volume (hereinafter sometimes referred to as "D90")-cumulative volume The secondary particle diameter D10 (hereinafter sometimes referred to as "D10") / D50] having a percentage of 10% by volume is not particularly limited, but when the positive electrode active material for alkaline storage batteries is used as a positive electrode, the positive electrode active material In the alkaline storage battery using the positive electrode active material as a positive electrode by reducing the gap between the positive electrode active material and the positive electrode active material, 0.85 or more is preferable from the viewpoint of being able to obtain excellent utilization at high temperatures and good volume capacity. 90 or more is especially preferable. On the other hand, the upper limit value of [(D90-D10) / D50] is not particularly limited, and an example is 1.20.

Next, an example of a method for producing a positive electrode active material for an alkaline storage battery of the present invention will be described.

As the above-mentioned production method, for example, a hydroxide particle containing nickel in which cobalt is dissolved is prepared, and a suspension containing hydroxide particles containing nickel in which cobalt is dissolved (for example, water suspension) By supplying a cobalt salt solution and an alkali solution to form a cobalt-containing coating on the surface of the nickel-containing nickel-doped cobalt particles, thereby forming the nickel-containing hydroxide particles. And a suspension (for example, a water suspension) containing hydroxide particles containing nickel on which the coating is formed, the nickel hydroxide including the nickel on which the coating is formed while the oxidation catalyst is in contact with the suspension. A gas containing oxygen is supplied to the suspension containing the substance particles in a microbubble generator to oxidize cobalt which has dissolved in the solid solution and cobalt contained in the coating layer.

Hereinafter, the details of the above-described example of the manufacturing method will be described. First, a salt solution (eg, a sulfate solution) of nickel, cobalt and another transition metal element (eg, magnesium, manganese, zinc and / or aluminum) is reacted with a complexing agent by coprecipitation method to form a solid solution Nickel-containing hydroxide particles (for example, particles in which divalent cobalt is dissolved in nickel hydroxide, nickel and other transition metal elements (for example, magnesium, manganese, zinc and / or aluminum)) And (ii) particles in which divalent cobalt is solid-solved in a hydroxide containing the (i) and (ii) to obtain a slurry-like suspension containing hydroxide particles containing nickel. As mentioned above, water is used as a solvent for the suspension, for example.

The complexing agent is not particularly limited as long as it can form a complex with an ion of nickel, cobalt or the other transition metal element in an aqueous solution, and examples thereof include ammonium ion donors (ammonium sulfate, ammonium chloride, Ammonium carbonate, ammonium fluoride, etc.), hydrazine, ethylenediaminetetraacetic acid, nitrilotriacetic acid, uracildiacetic acid, and glycine. In addition, in order to adjust the pH value of aqueous solution in the case of precipitation, you may add alkali metal hydroxide (for example, sodium hydroxide, potassium hydroxide) as needed.

When the complexing agent is continuously supplied to the reaction vessel in addition to the above-mentioned salt solution, nickel, cobalt and the other transition metal elements are reacted to produce hydroxide particles containing nickel solid-solved in cobalt. . During the reaction, the temperature of the reaction vessel is controlled, for example, in the range of 10 ° C. to 80 ° C., preferably 20 to 70 ° C., and the pH value in the reaction vessel is, for example, pH 9 to pH 13 at 25 ° C. The substance in the reaction vessel is appropriately stirred while controlling preferably in the range of pH 11 to 13. The reaction vessel may include, for example, a continuous system that overflows to separate the formed hydroxide particles containing nickel.

Next, a cobalt salt solution (eg, an aqueous solution of cobalt sulfate, etc.) and, if necessary, other transition metal elements (eg, magnesium, A salt solution of manganese, zinc and / or aluminum (for example, a sulfate solution) and an alkaline solution (for example, an aqueous solution of sodium hydroxide or the like) are added while stirring to form a solid solution of cobalt by neutralization crystallization. On the surface of the nickel-containing hydroxide particles, a coating containing cobalt compound such as cobalt hydroxide having a divalent valence of cobalt as a main component is formed. The pH of the step of forming the coating is preferably maintained in the range of pH 9 to 13 on a 25 ° C. basis. By the coating step, hydroxide particles containing nickel on which a coating layer containing cobalt is formed can be obtained. The hydroxide particle containing nickel in which the coating layer containing cobalt was formed can be obtained as a slurry-like suspension.

Next, while stirring the suspension containing the hydroxide particles containing nickel on which the coating layer is formed, the gas containing oxygen is supplied in the microbubble generator in the presence of the oxidation catalyst to perform the coating The divalent cobalt in the layer-formed nickel-containing hydroxide particles is oxidized to trivalent cobalt.

Examples of the oxidation catalyst may include, for example, compounds containing at least one metal selected from the group consisting of iron, nickel and chromium and / or ions of the metal, and specific examples include stainless steel. Can.

The average diameter of the oxygen-containing gas (bubbles) supplied by the microbubble generator is not particularly limited, but is, for example, preferably 1.0 μm or more and 50 μm or less, and particularly preferably 2.0 μm or more and 30 μm or less. By controlling the average diameter of the bubbles within the above range, it is possible not only to oxidize divalent cobalt contained in the coating layer to trivalent cobalt, but also to form a solid solution in nickel hydroxide particles. Cobalt can also be oxidized to trivalent cobalt more reliably. Examples of the gas containing oxygen include a gas containing oxygen, and a gas containing oxygen such as air and other elements.

As a micro bubble generating apparatus, YJ nozzle of Enviro-Vision, Inc. can be mentioned, for example.

The amount of oxygen (volume) of the oxygen-containing gas supplied to the suspension containing the hydroxide particles in which the coating layer is formed relative to the volume of the suspension containing hydroxide particles in which the coating layer is formed The ratio of is not particularly limited, but is adjusted to, for example, 1.00 or more and 2.55 or less. By setting it as the said range, bivalent cobalt solid-solved in the hydroxide particle containing nickel can be oxidized to trivalent cobalt efficiently and reliably.

In addition, if necessary, after the above-mentioned oxidation step, the suspension containing the oxidized hydroxide-containing nickel-containing hydroxide particles on which the covering layer is formed is separated into a solid phase and a liquid phase to obtain a liquid phase. The method may further include the step of drying the solid phase separated therefrom. In addition, before drying the solid phase, the solid phase may be washed with weakly alkaline water, if necessary. In addition, in order to obtain desired effects (high temperature characteristics and conductivity improvement, maintenance of conductive network), other transition metal elements (for example, ytterbium, yttrium, zirconium, tungsten, molybdenum, niobium, titanium, magnesium, etc., as needed. , Compounds of manganese, zinc and / or aluminum) (e.g. oxides) may be added in a known manner.

Next, a positive electrode using the positive electrode active material for an alkaline storage battery of the present invention and an alkaline storage battery using the positive electrode will be described. An alkaline storage battery is provided with the positive electrode using the positive electrode active material for alkaline storage batteries of this invention mentioned above, a negative electrode, alkaline electrolyte solution, and a separator.

The positive electrode includes a positive electrode current collector and a positive electrode active material layer formed on the surface of the positive electrode current collector. The positive electrode active material layer has a positive electrode active material for an alkaline storage battery, a binder (binding agent), and, as needed, a conductive aid. The conductive additive is not particularly limited as long as it can be used for, for example, an alkaline storage battery, and metallic cobalt, cobalt oxide, etc. can be used. The binder is not particularly limited, and polymer resins such as polyvinylidene fluoride (PVdF), butadiene rubber (BR), polyvinyl alcohol (PVA), carboxymethylcellulose (CMC), polytetrafluoroethylene (PTFE), etc., and A combination of these can be mentioned. Examples of the positive electrode current collector include, but are not particularly limited to, punching metal, expanded metal, wire mesh, foam metal such as foam nickel, reticulated metal fiber sintered body, metal plated resin plate and the like.

As a method of manufacturing a positive electrode, for example, first, a positive electrode active material for an alkaline storage battery, a conductive support agent, a binder and water are mixed to prepare a positive electrode active material slurry. Next, the positive electrode active material slurry is filled in a positive electrode current collector by a known filling method, dried, and then rolled and fixed by a press or the like.

The negative electrode includes a negative electrode current collector and a negative electrode active material layer including a negative electrode active material formed on the surface of the negative electrode current collector. The negative electrode active material is not particularly limited as long as it is usually used, and, for example, hydrogen storage alloy particles, cadmium oxide particles, cadmium hydroxide particles and the like can be used. As the negative electrode current collector, a conductive metal material such as nickel, aluminum, stainless steel, or the like, which is the same material as the positive electrode current collector, can be used.

Moreover, a conductive support agent, a binder, etc. may be further added to the negative electrode active material layer as needed. As a conductive support agent and a binder, the thing similar to what is used for the said positive electrode active material layer is mentioned.

As a method of manufacturing the negative electrode, for example, first, a negative electrode active material, and if necessary, a conductive auxiliary agent and a binder, and water are mixed to prepare a negative electrode active material slurry. Next, the negative electrode active material slurry is filled into a negative electrode current collector by a known filling method, dried, and then rolled and fixed by a press or the like.

As an alkaline electrolyte solution, water can be mentioned as a solvent, for example, As a solute dissolved in a solvent, potassium hydroxide, sodium hydroxide, lithium hydroxide can be mentioned, for example. The above solutes may be used alone or in combination of two or more.

The separator is not particularly limited, and examples thereof include polyolefin non-woven fabrics such as polyethylene non-woven fabrics, polypropylene non-woven fabrics, polyamide non-woven fabrics, and those obtained by subjecting them to hydrophilic treatment.

EXAMPLES Next, examples of the present invention will be described, but the present invention is not limited to these examples as long as the purpose of the present invention is not exceeded.

First, a suspension of cobalt hydroxide particles having no coating layer and a suspension of nickel hydroxide particles having a coating layer of cobalt hydroxide are each brought into contact with an oxidation catalyst, stainless steel, while being stirred. Further, air was supplied to carry out oxidation treatment, and cobalt hydroxide was changed to cobalt oxyhydroxide. In addition, although it becomes (gamma) -cobalt oxyhydroxide in the oxidation process which heats by adding an alkali to the said suspension, it is set as cobalt oxyhydroxide represented by chemical formula CoHO ₂ by performing the said oxidation process. Can. The physical properties of oxidized oxidized cobalt hydroxide particles without a coating layer (Experimental Example 1) and oxidized oxidized nickel hydroxide particles with a coated layer of cobalt hydroxide (Experimental Example 2) are shown in Table 1 below. Shown in.

The X-ray diffraction measurement was performed on the samples of Experimental Example 1 and Experimental Example 2 and cobalt oxyhydroxide to analyze diffraction peaks.
The X-ray diffraction measurement was performed under the following conditions using an X-ray diffraction apparatus (Rigaku, Ultima IV).
X-ray: CuKα / 40kV / 40mA
Slit: divergence = 1/2 °, light reception = open, scattering = 8.0 mm
Sampling width: 0.03
Scan speed: 20 ° / min

The results of X-ray diffraction measurement of the samples of Experimental Example 1 and Experimental Example 2 and cobalt oxyhydroxide are shown in FIG. 1 and FIG.

As shown in FIGS. 1 and 2, in each of the samples of Experimental Example 1 and Experimental Example 2 and cobalt oxyhydroxide, there is a diffraction peak between diffraction angles of 65 ° to 66 ° represented by 2θ of the diffraction pattern. Admitted. Therefore, it was confirmed that the diffraction peak between diffraction angles of 65 ° to 66 ° represented by 2θ is a peak unique to cobalt oxyhydroxide (that is, trivalent cobalt represented by the chemical formula CoHO ₂ ) .

Example 1
Synthesis of hydroxide particles containing nickel in solid solution of cobalt An aqueous solution of ammonium sulfate (complexing agent) and an aqueous solution of sodium hydroxide are dropped into an aqueous solution in which magnesium sulfate, cobalt sulfate and nickel sulfate are dissolved at a predetermined ratio, Stirring was continuously performed with a stirrer while maintaining the pH in the reaction vessel at 12.2 at 25 ° C. The formed hydroxide overflowed from the overflow pipe of the reaction vessel and was taken out. Each of the removed hydroxides was subjected to water washing, dehydration, and drying to obtain hydroxide particles containing nickel in which cobalt is dissolved.

Formation of a Coating Layer Containing Cobalt A reaction in which hydroxide particles containing nickel in which solid solution of cobalt was obtained as described above was maintained with sodium hydroxide in the range of 9 to 13 at a liquid temperature of 25 ° C. It was poured into an alkaline aqueous solution in the bath. After the addition, while stirring the solution, an aqueous solution of cobalt sulfate having a concentration of 90 g / L was dropped. During this time, an aqueous solution of sodium hydroxide is suitably added dropwise to maintain the pH of the reaction bath within the range of 9 to 13 with a liquid temperature of 25 ° C. to form a cobalt hydroxide coating layer on the surface of the hydroxide particles. Thus, a suspension of hydroxide particles containing cobalt-solidified nickel covered with cobalt hydroxide was obtained.

Oxidizing treatment of cobalt hydroxide-coated nickel solution-containing hydroxide particles containing cobalt, obtained as described above, cobalt hydroxide-coated cobalt solutiond nickel-containing hydroxides The suspension of substance particles is brought into contact with the oxidation catalyst, stainless steel, while being stirred, and air is further supplied to the suspension in a microbubble generator (Enviro Vision Inc., “YJ nozzle”) to oxidize it. I did the processing. Further, the ratio of the volume of oxygen contained in the air to the volume of the suspension of hydroxide particles containing cobalt in which solid solution of cobalt is covered with cobalt hydroxide is 1.28, Air was supplied to the above suspension. In the above oxidation treatment, cobalt dissolved in nickel hydroxide particles and cobalt hydroxide in the covering layer were oxidized to form cobalt oxyhydroxide which is trivalent cobalt.

Solid-Liquid Separation and Drying Next, the oxidized suspension was subjected to water washing, dehydration, and drying to obtain cobalt-containing compound-coated nickel-containing hydroxide particles of Example 1. The physical properties of the cobalt-containing compound-coated nickel-containing hydroxide particles of Example 1 are shown in Table 2 below. In Examples and Comparative Examples of Table 2, after all the cobalt in the coating layer is oxidized to trivalent cobalt, cobalt dissolved as a solid solution in nickel hydroxide particles is oxidized. The amount of oxidized cobalt (Co (III)) dissolved in substance particles was specified. The physical properties of the cobalt-containing compound-coated nickel-containing hydroxide particles of Example 1 are shown in Table 2 below.

Comparative Example 1
By replacing the pH in the reaction tank with 12.2 at a liquid temperature of 25 ° C. in Example 1, the pH in the reaction tank was maintained at 12.0 with a liquid temperature of 25 ° C. A cobalt-containing compound-coated nickel-containing hydroxide particle of Comparative Example 1 having a particle size distribution different from that of Example 1 was obtained. The physical properties of the cobalt-containing compound-coated nickel-containing hydroxide particles of Comparative Example 1 are shown in Table 2 below.

In Table 2,
The component composition was analyzed using an ICP emission analyzer (Perkin-Elmer, Optima (registered trademark) 8300). The value obtained by subtracting the Co content of cobalt-containing nickel-containing hydroxide particles from the Co content of the cobalt-containing compound-coated nickel-containing hydroxide particles is taken as the Co content of the coating layer.
The BET specific surface area was measured by a one-point BET method using a specific surface area measuring device (Muntech Inc., Macsorb (registered trademark)).
As a classifier, using a classifier (Nittetsu Mining Co., Ltd., Elbow jet classifier EJ-L-3), the classification edge distance M is 41.0 mm, the classification edge distance F is 30.0 mm, and the air pressure is 0.5 Mpa. After setting, the measurement particles were fed by feed air and classified.
D5, D10, D50, D90, and D95 were measured by a particle size distribution analyzer (Horiba, Ltd., LA-950) (the principle is a laser diffraction / scattering method). Further, the value of the particle size distribution width (D90-D10) / D50 was calculated from the measured values of D10, D50, D90.

The diffraction peak was analyzed by performing X-ray diffraction measurement on Example 1 and Comparative Example 1 and cobalt oxyhydroxide. The X-ray diffraction measurement was performed in the same manner as in Experimental Example 1 and Experimental Example 2 above.

The results of X-ray diffraction measurement for Example 1 and Comparative Example 1 and cobalt oxyhydroxide are shown in FIGS. 3 and 4.

As shown in FIGS. 3 and 4, in each of Example 1 and Comparative Example 1, a diffraction peak was observed between diffraction angles of 65 ° to 66 ° represented by 2θ of the diffraction pattern. Therefore, in Example 1 and Comparative Example 1, at least a part of cobalt dissolved in nickel hydroxide particles is dissolved as cobalt oxyhydroxide which is trivalent cobalt, and the coating layer is oxidized It was confirmed to have cobalt.

The physical properties of the samples of D10 or less, D50, D90 or more among Example 1 and Comparative Example 1 are shown in Table 3 below.

Preparation of Positive Electrode The particles of each Example or Comparative Example which is a positive electrode active material by the solid content mass ratio: PTFE (polytetrafluoroethylene) as a binder: water = 80: 10: 10 The slurry-like composition was produced by mixing, PTFE, and water. The thus prepared slurry composition was filled in foamed nickel (current collector), dried and rolled, to prepare each positive electrode.

Preparation of Evaluation Cell The positive electrode to which the sample of each of the above-described Examples or Comparative Examples was added, a hydrogen storage alloy was used for the negative electrode, and a polyolefin non-woven fabric composed of polyethylene and polypropylene for the separator was used. Furthermore, using an electrolytic solution containing 6 mol / L of KOH as an electrolytic solution, an evaluation cell was assembled, and the following items were evaluated.

(1) Normal Temperature (25 ° C.) Charge / Discharge Capacity Test The above evaluation cell was stored at 25 ° C. for 12 hours, charged at 0.2 C for 6 hours, and then discharged at 0.2 C to 1.0 V. This operation was repeated 10 times to activate. The charge capacity at normal temperature was taken as the discharge capacity at the 10th activation.

(2) High temperature (60 ° C.) charge and discharge capacity test After storing the activated cell at 60 ° C. for 4 hours, charge at 0.2 C for 5 hours while keeping the temperature at 60 ° C. The discharge capacity was measured when discharged to 1.0 V.

The evaluation results of the alkaline storage batteries using the samples of Example 1 and Comparative Example 1 as the positive electrode are shown in Table 4 below.

As shown in Table 2 above, the content of trivalent cobalt in the solid solution cobalt is 30% by mass or more, and as shown in Tables 3 and 4 above, the solid content of the positive electrode active material for alkaline storage batteries The ratio of the content of trivalent cobalt in solid solution of the positive electrode active material particles for alkaline storage batteries of D10 or less to the content of dissolved trivalent cobalt in the positive electrode active material for alkaline storage batteries is 0.981 (that is, , 0.80 or more and 1.20 or less), the ratio of the content rate of trivalent cobalt in solid solution among the positive electrode active material particles for alkaline storage batteries of D90 or more is 1.111 (that is, 0.80 or more and 1.20 or less) In Example 1 which is), it was possible to obtain excellent utilization at high temperature (60 ° C.) while having excellent utilization at normal temperature (25 ° C.). Further, as shown in Table 2, in Example 1, the value of the particle size distribution width (D90-D10) / D50 was 0.91.

On the other hand, among the positive electrode active materials for alkaline storage batteries with respect to the content rate of solid solution trivalent cobalt of the positive electrode active materials for alkaline storage batteries, solid solutions for trivalent of positive electrode active material particles for alkaline storage batteries of D10 or less In Comparative Example 1 in which the ratio of the content of cobalt was 1.615, the utilization was good at normal temperature (25 ° C.), but a good utilization could not be obtained at high temperature (60 ° C.).

The positive electrode active material for an alkaline storage battery of the present invention exerts an excellent utilization factor even under high temperature conditions, and thus has high utility value in the field of a positive electrode active material of an alkaline storage battery that can be used in high temperature environments such as vehicles.

Claims (5)

A positive electrode active material for an alkaline storage battery, comprising: nickel-containing hydroxide particles containing dissolved cobalt; and a cobalt-containing coating layer coating the hydroxide particles,
It has a diffraction peak between the diffraction angle 65 ° to 66 ° represented by 2θ of the diffraction pattern obtained by X-ray diffraction measurement,
The content of trivalent cobalt in the solid-solved cobalt is 30% by mass or more,
Of the positive electrode active material for an alkaline storage battery relative to the content of the trivalent cobalt in solid solution of the positive electrode active material for an alkaline storage battery, the secondary particle diameter (≦ D10) having a cumulative volume percentage of 10.0 volume% or less The secondary particle diameter of 0.80 or more and 1.20 or less and a cumulative volume percentage of 90.0% by volume or more of the content of the solid solution of trivalent cobalt contained in the positive electrode active material particles for alkaline storage batteries of The positive electrode active material for alkaline storage batteries whose ratio of content rate of said trivalent cobalt which carried out the solid solution of the positive electrode active material particles for alkaline storage batteries of (> = D90) is 0.80 or more and 1.20 or less. The positive electrode active material for an alkaline storage battery according to claim 1, wherein the diffraction peak is derived from a trivalent cobalt compound represented by CoHO ₂ . [Secondary particle diameter (D90) of the positive electrode active material for an alkaline storage battery having a cumulative volume percentage of 90.0% by volume-secondary particle diameter of the positive electrode active material for an alkaline storage battery having a cumulative volume percentage of 10.0% by volume (D90) D10) The positive electrode active for an alkaline storage battery according to claim 1 or 2, wherein the secondary particle diameter (D50) of the positive electrode active material for an alkaline storage battery having a cumulative volume percentage of 50.0% by volume is 0.85 or more. material. The positive electrode which has a positive electrode active material for alkaline storage batteries of any one of Claims 1 thru | or 3. An alkaline storage battery comprising the positive electrode according to claim 4.

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